In recent years, along with a variety of electronic apparatuses becoming more compact, an electronic device to be installed in an electronic apparatus has become more compact and higher in performance. A multilayer ceramic capacitor as one of the electronic devices is also expected to be more compact and higher in performance.
For pursuing a more compact multilayer ceramic capacitor having a larger capacity, there has been a strong demand for a thinner dielectric layer. Recently, a thickness of a dielectric green sheet has come to several μm or thinner.
To produce a ceramic green sheet, ceramic slurry made by ceramic powder, a binder (an acrylic based resin and a butyral resin, etc.), a plasticizer and an organic solvent (toluene, alcohol and MEK, etc.) is normally prepared first, then, the ceramic slurry is applied to a carrier sheet, such as PET, by using the doctor blade method, etc. and dried by heating.
Also, in recent years, a production method of preparing ceramic suspension obtained by mixing ceramic powder and a binder in a solvent, and performing 2-dimensional drawing on a film-shaped mold obtained by extrusion molding of the suspension has been studied.
A method of producing a multilayer ceramic capacitor by using the ceramic green sheet explained above will be explained specifically. An internal electrode conductive paste including metal powder and a binder is printed to be a predetermined pattern on the ceramic green sheet and dried to form an internal electrode pattern. Next, a carrier sheet is released from the ceramic green sheet, a plurality of the results are stacked and cut to be a chip shape, so that a green chip is obtained. Next, after firing the green chip, an external electrode is formed, and the multilayer ceramic capacitor is produced.
In recent years, as a use range of a multilayer ceramic capacitor increases, a small size with a large capacity has become a demand in the market. To respond thereto, an interlayer thickness of sheets formed with an internal electrode has become steadily thinner each year.
However, in the case of printing the internal electrode paste on an extremely thin ceramic green sheet, there is a disadvantage that a binder component in the ceramic green sheet is dissolved or swollen due to a solvent in the internal electrode paste. Also, there is a disadvantage that an internal electrode paste soaks in the green sheet. These disadvantages often cause a short-circuiting defect.
To eliminate the disadvantages, in the Japanese Unexamined Patent Publication Nos. 63-51616, 3-250612 and 7-312326, a dry type electrode pattern is separately prepared by forming an internal electrode pattern on a supporting sheet and drying the same. An internal electrode pattern transfer method for transferring the dry type electrode pattern to a surface of each ceramic green sheet or a surface of a multilayer body of ceramic green sheets has been proposed.
In the technique disclosed in these publications, however, particularly when a thickness of the green sheet is thin, it is extremely difficult to bond the electrode pattern layer with a surface of a green sheet to transfer with high accuracy and a ceramic green sheet is partially broken in the transfer step in some cases.
Also, in the transfer method according to these conventional techniques, since a high pressure and heat are necessary to transfer the electrode pattern layer to the surface of the green sheet, the green sheet, electrode layer and supporting sheet often deform and become unable to be used at the time of stacking, and there is a possibility of causing a short-circuiting defect due to break of the green sheet.
Note that a method of forming an adhesive layer on a surface of the electrode layer or green sheet is considered for easier transfer of the electrode layer. However, when forming an adhesive layer directly on the surface of the electrode layer or green sheet by a coating method, etc., components of the adhesive layer soak in the electrode layer or green sheet. Therefore, a function as an adhesive layer is hard to be attained, and it is liable that a composition of the electrode layer or green sheet is adversely affected.
Also, the Japanese Unexamined Patent Publication No. 2001-23853 discloses a production method of stacking multilayer blocks via an adhesive layer (adherence layer). However, in the method described in this article, a thickness of the adhesive layer is thick as 0.5 to 5 μm and it is not suitable as an adhesive layer for transferring an electrode layer to an extremely thin green sheet.